/**
 * @(#)CollectionUtils.java
 *
 * Copyright (c) 2010 sinba. All Rights Reserved.
 */
package com.sinba.common.util;

import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;


/**
 * Miscellaneous collection utility methods.
 * Mainly for internal use within the framework.
 *
 * @version 1.00 2007-4-23
 * @author <a href="mailto:sinbawang@msn.com">Sinba Wang</a>
 */
@SuppressWarnings("unchecked")
public abstract class CollectionUtils {

    /**
     * protected constructor.
     */
    protected CollectionUtils() {

    }

    /**
     * Return <code>true</code> if the supplied Collection is <code>null</code>
     * or empty. Otherwise, return <code>false</code>.
     * @param collection the Collection to check
     * @return whether the given Collection is empty
     */
    public static boolean isEmpty(Collection collection) {

        return ((collection == null) || collection.isEmpty());
    }

    /**
     * Return <code>true</code> if the supplied Map is <code>null</code>
     * or empty. Otherwise, return <code>false</code>.
     * @param map the Map to check
     * @return whether the given Map is empty
     */
    public static boolean isEmpty(Map map) {

        return ((map == null) || map.isEmpty());
    }

    /**
     * Convert the supplied array into a List. A primitive array gets
     * converted into a List of the appropriate wrapper type.
     * <p>A <code>null</code> source value will be converted to an
     * empty List.
     * @param source the (potentially primitive) array
     * @return the converted List result
     * @see ObjectUtils#toObjectArray(Object)
     */
    public static List arrayToList(Object source) {

        return Arrays.asList(ObjectUtils.toObjectArray(source));
    }

    /**
     * Merge the given array into the given Collection.
     * @param array the array to merge (may be <code>null</code>)
     * @param collection the target Collection to merge the array into
     */
    public static void mergeArrayIntoCollection(Object array,
        Collection collection) {

        if (collection == null) {

            throw new IllegalArgumentException(
                "Collection must not be null");
        }

        Object[] arr = ObjectUtils.toObjectArray(array);

        for (int i = 0; i < arr.length; i++) {

            collection.add(arr[i]);
        }
    }

    /**
     * Merge the given Properties instance into the given Map,
     * copying all properties (key-value pairs) over.
     * <p>Uses <code>Properties.propertyNames()</code> to even catch
     * default properties linked into the original Properties instance.
     * @param props the Properties instance to merge (may be <code>null</code>)
     * @param map the target Map to merge the properties into
     */
    public static void mergePropertiesIntoMap(Properties props, Map map) {

        if (map == null) {

            throw new IllegalArgumentException("Map must not be null");
        }

        if (props != null) {

            for (Enumeration en = props.propertyNames();
                    en.hasMoreElements();) {

                String key = (String) en.nextElement();

                map.put(key, props.getProperty(key));
            }
        }
    }

    /**
     * Check whether the given Iterator contains the given element.
     * @param iterator the Iterator to check
     * @param element the element to look for
     * @return <code>true</code> if found, <code>false</code> else
     */
    public static boolean contains(Iterator iterator, Object element) {

        if (iterator != null) {

            while (iterator.hasNext()) {

                Object candidate = iterator.next();

                if (ObjectUtils.nullSafeEquals(candidate, element)) {

                    return true;
                }
            }
        }

        return false;
    }

    /**
     * Check whether the given Enumeration contains the given element.
     * @param enumeration the Enumeration to check
     * @param element the element to look for
     * @return <code>true</code> if found, <code>false</code> else
     */
    public static boolean contains(Enumeration enumeration, Object element) {

        if (enumeration != null) {

            while (enumeration.hasMoreElements()) {

                Object candidate = enumeration.nextElement();

                if (ObjectUtils.nullSafeEquals(candidate, element)) {

                    return true;
                }
            }
        }

        return false;
    }

    /**
     * Check whether the given Collection contains the given element instance.
     * <p>Enforces the given instance to be present, rather than returning
     * <code>true</code> for an equal element as well.
     * @param collection the Collection to check
     * @param element the element to look for
     * @return <code>true</code> if found, <code>false</code> else
     */
    public static boolean containsInstance(Collection collection,
        Object element) {

        if (collection != null) {

            for (Iterator it = collection.iterator(); it.hasNext();) {

                Object candidate = it.next();

                if (candidate == element) {

                    return true;
                }
            }
        }

        return false;
    }

    /**
     * Return <code>true</code> if any element in '<code>candidates</code>' is
     * contained in '<code>source</code>'; otherwise returns <code>false</code>.
     * @param source the source Collection
     * @param candidates the candidates to search for
     * @return whether any of the candidates has been found
     */
    public static boolean containsAny(Collection source,
        Collection candidates) {

        if (isEmpty(source) || isEmpty(candidates)) {

            return false;
        }

        for (Iterator it = candidates.iterator(); it.hasNext();) {

            if (source.contains(it.next())) {

                return true;
            }
        }

        return false;
    }

    /**
     * Return the first element in '<code>candidates</code>' that is contained in
     * '<code>source</code>'. If no element in '<code>candidates</code>' is present in
     * '<code>source</code>' returns <code>null</code>. Iteration order is
     * {@link Collection} implementation specific.
     * @param source the source Collection
     * @param candidates the candidates to search for
     * @return the first present object, or <code>null</code> if not found
     */
    public static Object findFirstMatch(Collection source,
        Collection candidates) {

        if (isEmpty(source) || isEmpty(candidates)) {

            return null;
        }

        for (Iterator it = candidates.iterator(); it.hasNext();) {

            Object candidate = it.next();

            if (source.contains(candidate)) {

                return candidate;
            }
        }

        return null;
    }

    /**
     * Find a value of the given type in the given Collection.
     * @param collection the Collection to search
     * @param type the type to look for
     * @return a value of the given type found, or <code>null</code> if none
     */
    public static Object findValueOfType(Collection collection, Class type) {

        if (isEmpty(collection)) {

            return null;
        }

        Class typeToUse = ((type != null) ? type : Object.class);
        Object value = null;

        for (Iterator it = collection.iterator(); it.hasNext();) {

            Object obj = it.next();

            if (typeToUse.isInstance(obj)) {

                if (value != null) {

                    throw new IllegalArgumentException(
                        "More than one value of type ["
                        + typeToUse.getName() + "] found");
                }

                value = obj;
            }
        }

        return value;
    }

    /**
     * Find a value of one of the given types in the given Collection:
     * searching the Collection for a value of the first type, then
     * searching for a value of the second type, etc.
     * @param collection the collection to search
     * @param types the types to look for, in prioritized order
     * @return a of one of the given types found, or <code>null</code> if none
     */
    public static Object findValueOfType(Collection collection,
        Class[] types) {

        if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {

            return null;
        }

        for (int i = 0; i < types.length; i++) {

            Object value = findValueOfType(collection, types[i]);

            if (value != null) {

                return value;
            }
        }

        return null;
    }

    /**
     * Determine whether the given Collection only contains a single unique object.
     * @param collection the Collection to check
     * @return <code>true</code> if the collection contains a single reference or
     * multiple references to the same instance, <code>false</code> else
     */
    public static boolean hasUniqueObject(Collection collection) {

        if (isEmpty(collection)) {

            return false;
        }

        boolean hasCandidate = false;
        Object candidate = null;

        for (Iterator it = collection.iterator(); it.hasNext();) {

            Object elem = it.next();

            if (!hasCandidate) {

                hasCandidate = true;
                candidate = elem;
            } else if (candidate != elem) {

                return false;
            }
        }

        return true;
    }
}